code: def test_concave_decreasing():
      """Tests that a correct knee point is detected in
      curve having concave and decreasing nature."""
      kn = KneeLocator(
          x,
          y_concave_dec,
          curve_nature="concave",
          curve_direction="decreasing",
      )
      assert kn.knee == 7
  
file_path: yellowbrick/tests/test_utils/test_kneed.py
imports: import pytest
  import matplotlib.pyplot
  import numpy
  from yellowbrick.utils.kneed import KneeLocator
label_desc: Use image node_id 2 for calling a global function with example usage: test_concave_decreasing() without return types